Method of spreading particles and spreading apparatus

ABSTRACT

The present invention is a method for spreading spacing particles on a surface of a substrate used to form a liquid crystal display panel. The method comprises the steps of relatively moving the substrate and a spreading nozzle with respect to one another as the spreading nozzle spread the spacing particles such that the spacing particles spread from the spreading nozzle trace a predetermined trace on the surface of the substrate. Electric charge on the substrate is discharged while relatively moving the substrate and the spreading nozzle such that the spreading nozzle spreads the spacing particles on a discharged portion of the surface of the substrate.

BACKGROUND OF THE INVENTION

The present invention relates to a method of spreading particles betweentwo substrates of a liquid crystal display panel such that the particlesserve as spacers for controlling the distance between the substrates.

In recent years, demands have arisen for a liquid crystal display panelwith high performance qualities such as high contrast, a wide viewangle, etc., and with high display enough quality to create a uniformdisplay image over the entire display element without defects.

In general, a liquid crystal display panel is constructed in a manner inwhich two substrates are arranged so as to face each other and liquidcrystal is enclosed between these substrates. It is essential to bothhigh performance and high display quality to maintain a uniform distancebetween the two opposite substrates. Specifically, it is necessary tomaintain the distance between the substrates at a predetermined value inorder to achieve high performance of the liquid crystal display element.It is also necessary to keep the distance between the substrates uniformover the entire areas of the substrates in order to further achieve highdisplay quality.

Hence, in order to obtain a uniform substrate distance over the entireareas of the substrates, a method has been adopted in which spacersconsisting of particles each having a desired diameter are uniformlyspread on the surface of one of the substrates and the other substrateis thereafter adhered thereon.

For example, Japanese Patent Application KOKAI Publication No. 6-3679discloses an apparatus for spreading spacers comprising a swingablespreading nozzle for spreading spacers and a movement mechanism forrelatively moving the spreading nozzle and a substrate in the X- andY-directions in a horizontal plane. In this apparatus, spacers arespread onto the substrate from the nozzle while relatively moving thespreading nozzle and the substrate such that an extended line of thecenter axis of the spreading nozzle draws a saw-tooth-like zigzag traceon the substrate.

However, according to such a conventional spreading apparatus and amethod thereof as described above, the distance between parts of thetrace is smaller at each folded portion so that the spread areas ofparticles on the substrate are overlapped at the folded portions of thetrace. In these overlapped areas, the amount of the spacers thussupplied is larger and the spread density is higher than in the otherareas. For example, in case where spacers each having a diameter ofabout 5 μm is spread at a spread density of about 150 particles/mm², thespread density is increased to 150 to 170 particles/mm² in theoverlapped areas. Therefore, the spread density of the spacers on thesubstrate is not uniform so that it is difficult to maintain a uniformdistance between two substrates.

Note that the trace of spread particles means the trace of movement ofthe center of distribution of spread particles, i.e., the trace of across point between an extended line of the center axis of the spreadingnozzle for spreading particles and the surface of the substrate.

In order to prevent the spread density from being not uniform, the swingangle of the spreading nozzle may be increased so as to make foldedportions of the trace be positioned outside the substrate. However, theamount of spacers used will then be increased and the time required forspreading will be elongated.

Furthermore, in a method of spreading spacers through a spreadingnozzle, the spacers are electrically charged by friction caused as thespacers transferred through a convey path with positive or negativeelectric charges. This kind of charging of the spacers may be preferablein view of preventing the spacers from being coagulated. If the spacersthus electrically charged are spread onto the substrate, a number oflines such as scanning lines, signal lines, and a short ring formed onthe substrate are also electrically charged to a potential equal to thespacers.

However, since complicated electronic circuits are provided on thesubstrate of a liquid crystal panel, the substrate is not uniformlycharged over its entire region, but only several particular lines or thelikes are charged. In particular, when spacers are spread while movingthe spreading nozzle so as to draw a certain trace, particular lines orthe like on that region of the substrate where spacers are not yetspread are charged to a potential equal to the potential of the spacers,and those lines or the like repulses spacers which are spread later onthat region. Therefore, the spread density of the spacers on such aregion of the substrate is decreased abnormally so that non-uniformityoccurs.

In addition, electric charges are gradually applied to the lines and thelike of the substrate as spacers are gradually spread on the substrate.Thus, charging of the substrate leads to occurrence of defects such aselectrostatic breakdown or the like of the electronic circuit and istherefore not desirable.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstances,and its object is to provide a method of spreading particles capable ofuniformly spreading particles serving as spacers onto a substrate.

In order to achieve the above object, a method is provided for spreadingspacing particles on a surface of a substrate used to form a liquidcrystal display. The method comprises the steps of relatively moving thesubstrate and a spreading nozzle adapted to spread the spacing particleson the substrate with respect to one another as the spreading nozzlespreads the spacing particles such that the spacing particles spreadfrom the spreading nozzle (draw a zigzag) to form a predetermined traceon the surface of the substrate. Electric charges on the substrate aredischarged while relatively moving the substrate and the spreadingnozzle such that the spreading nozzle spreads the spacing particles on adischarged portion of the surface of the substrate.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention and, together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIGS. 1 to 3 show a spreading apparatus according to an embodiment ofthe present invention, in which:

FIG. 1 is a schematic view showing the entire spreading apparatus,

FIG. 2 is a perspective view showing a movable table, a discharging bar,and a spreading nozzle of the apparatus, and

FIG. 3 is a side view showing a positional relationship between thedischarging bar and the spreading nozzle;

FIG. 4 is a perspective view of a glass substrate used for manufacturingarray substrates of liquid crystal display panels;

FIG. 5 is an enlarged plan view showing a part of conductive patternformed on the glass substrate; and

FIG. 6 is a plan view schematically showing a trace of the spreadingnozzle in relation to a substrate.

DETAILED DESCRIPTION OF THE INVENTION

In the following, an embodiment of the present invention will bespecifically explained.

FIGS. 1 to 3 show a spreading apparatus for spreading particles servingas spacers onto a glass substrate 10 used for manufacturing liquidcrystal display panels.

As shown in FIG. 4, the glass substrate 10 formed in a rectangular shapeand has a size corresponding to six array substrates used for liquidcrystal display panels. Six conductive patterns 40 for the arraysubstrates are formed on the surface of the glass substrate 10 withpredetermined intervals.

As shown in FIG. 5, each of the conductive pattern 40 includes a numberof signal lines 42 and a number of scanning lines 44 which are arrangedin matrix and serve as conductive lines. A pixel electrode 46 isarranged in each region enclosed by the signal and scanning lines 42 and44 and is connected to these lines through a thin film transistor 45.Further, the conductive pattern 40 has a rectangular short ring 48 towhich the signal and scanning lines 42 and 44 are connected. On theglass substrate 10, a sealing agent 50 is pasted so as to surround eachof the conductive patterns 40.

As shown in FIGS. 1 to 3, the spreading apparatus includes a container12 which defines a spreading space for spreading spacers, partitionedfrom the outside, and a support base 14 provided in the container 12. Amovable table 16 for mounting the glass substrate 10 is arranged on thesupport base 14, such that the table is movable in a X-directionparallel to a longitudinal side of the glass substrate 10. The movabletable 16 is moved at a predetermined speed by means of a movingmechanism 18 having a motor (not shown), a transmission mechanism andthe like. The movable table 16 is connected to the ground of thespreading apparatus.

In addition, a discharging bar 20 extending in a Y-directionperpendicular to the X-direction is provided on the support base 14 suchthat the bar 20 is located over the movable table 16 and faces parallelwith the surface of the glass substrate 10 on the table 16.

In the container 12, a swingable spreading nozzle 22 is provided abovethe movable table 16. The spreading nozzle 22 is driven to swing at adesired angle and an arbitrary angle speed in the Y-direction by anozzle drive mechanism 24 provided on the container 12. Further, thespreading nozzle 22 is disposed to shift in the moving direction (orX-direction) of the movable table 16 with respect to the discharging bar20. The distance d between the spreading nozzle 22 and the dischargingbar 20 in the X-direction is set to be shorter than the length of theglass substrate 10 in the X-direction and to be also as short aspossible without causing the discharging bar 20 to interfere with thespreading operation. Specifically, the spreading nozzle 22 and thedischarging bar 20 are arranged such that both of the spreading nozzle22 and the discharging bar 20 are at least temporarily opposed to theglass substrate 10 while the glass substrate 10 is moved in theX-direction by the movable table 16.

Note that the movable table 16, the moving mechanism 18, and the drivemechanism 24 constitute a moving means in the present invention.

The spreading nozzle 22 is connected through a feed tube 26 to a feeddevice 28 for supplying particles. The feed device 28 comprises a spacerstorage portion, a compressor also not shown, a shut-off valve, and thelike (not shown). The spacer storage portion contains spacers consistingof resin balls each having a diameter of about 5 μm. The compressorsupplies the spacers from the spacer storage portion to the spreadingnozzle 22 through the feed tube 26 by air pressure and spreads thespacers from the spreading nozzle 20. In addition, a blower 30 forexhausting air in the container 12 is connected to the bottom portion ofthe container 12.

Each of the moving mechanism 28, the discharging bar 20, the nozzledrive mechanism 24, and the feed device 28 is connected to a controlsection 32 serving as control means. The operation of these componentsis controlled by the control section 32. For example, the nozzle drivemechanism 24 is capable of changing the swing angle and the angle speedof the spreading nozzle 22 under the control by the control section 32.Further, the feed device 28 is capable of arbitrarily setting the supplyamount of the spacers per unit time, also under the control by thecontrol section 32.

Next will be explained a method of spreading spacers onto the surface ofthe array substrate 10 by means of the spreading apparatus constructedas described above.

At first, a glass substrate 10 is placed on a movable table 16, with thelengthwise axis or the longitudinal sides of the glass substrate 10oriented in the X-direction. The glass substrate 10 is conducted to theground of the spreading apparatus through the movable table 16.Subsequently, under the control by the control section 32, the movabletable 16 is moved in the X-direction at a predetermined constant speedby the moving mechanism 18, and the spreading nozzle 22 is made swing inthe Y-direction at a predetermined angle speed.

In this manner, the glass substrate 10 on the movable table 16 moves inthe X-direction from one end side of the substrate 10, passing below thedischarging bar 20 and below the spreading nozzle 22. The glasssubstrate 10 and the spreading nozzle 22 move in relation to each otherin the X- and Y-directions in a horizontal plane. Therefore, as shown inFIGS. 2 and 6, an extended line of the center axis of the spreadingnozzle 22 moves drawing a saw-tooth-like zigzag trace A on the surfaceof the glass substrate 10. Note that the swing angle of the spreadingnozzle 22 is set such that each of folded portions B of the trace Asubstantially corresponds with either of both side edges of the glasssubstrate 10.

Meanwhile, in synchronization with driving of the nozzle drive mechanism24 and the moving mechanism 18, the discharging bar 20 is energizedunder the control of the control section 32, and simultaneously, thefeed device 28 and the blower 30 are driven.

In this manner, as the glass substrate 10 passes below the dischargingbar 20, the region of the glass substrate 10 which has faced thedischarging bar 20 is sequentially discharged. The spacers supplied fromthe spreading nozzle 22 are charged to a potential of about -5 to 10 kVby frictional charging or the like when they pass through the feed tube26 and the spreading nozzle 22. Thus, the conductive patterns 40 on theglass substrate 10 are charged to a potential by the supplied spacerswhen discharging is not performed. By discharging the glass substrate 10by means of the discharging bar 20, the potential of each conductivepattern 40 is discharged to a potential of substantially zero which issubstantially lower than the charge of the spacers.

Further, the spacers are supplied to the spreading nozzle 22 through thefeed tube 26 from the feed device 28 and are spread toward the surfaceof the glass substrate 10 from the spreading nozzle 22. Here, thespacers are spread with a predetermined width along the trace A of thespreading nozzle 22, onto that region of the glass substrate 10 whichhas been subjected to discharging by the discharging bar 20.

In addition, upon spreading the spacers, the control section 32 changesthe spreading amount of the spacers in correspondence with the movingposition of the spreading nozzle 22. Specifically, when the spreadingnozzle 22 passes each of folded portions B of the trace A, e.g., whenthe spreading nozzle 22 passes the region outside each of circle marksin FIG. 6, the control section 32 reduces the supply amount of thespacers from the feed device 28 to a predetermined amount. Supposingthat the spacer supply amount which will achieve a normal spread densityof 150 particles/mm² is expressed as an index of 100, the spacer supplyamount is reduced to an index of 50 to 70 when the nozzle 22 passesthrough each of the folded portions B.

For example, when the size of the glass substrate 10 is set to 550×650mm, the angle speed of the spreading nozzle 22 is 15 rpm, and the swingangle is 60 degrees.

According to the spreading apparatus and the spreading method asconstructed above, during the steps of spreading spacers from thespreading nozzle 22 while relatively moving the nozzle with respect tothe glass substrate 10 so as to draw the zigzag trace A on the surfaceof the glass substrate 10, the spreading amount of the spacers spreadfrom the spreading nozzle 22 is decreased at the folded portions of thetrace, i.e., at the portions where the distance between parts of thetrace including a folded portion is small. Therefore, the spreadingdensity in the region where the distance between those parts of thetrace is small is not higher than the other parts of the trace, therebyspreading the spacers with a uniform density over the entire surface ofthe glass substrate 10.

In addition, it is not necessary to position folded portions B of thetrace A outside the glass substrate 10, thereby reducing the amount ofspacers consumed from to 1/2 to 2/3 in comparison with the amount ofspacers consumed when the spacers are continuously spread at a constantrate. Thus, the present invention improves economical efficiency.

Further, since the spacers are spread while discharging the glasssubstrate 10 by means of the discharging bar 20, the potential of theconductive patterns 40 in the region which is continuous to the spreadregion on the glass substrate and in which the spacers are not yetspread, is prevented from being charged to a potential equal to thespacers to be spread on the glass substrate. Therefore, spacers can besmoothly spread onto the region which has been discharged to a potentialdifferent to the potential of the spacers, i.e., discharged to theground, so that the spread spacers are prevented from being repelled andscattered by the conductive patterns 40. As a result, it is possible toprevent non-uniform spreading of spacers, and spacers can be spread at auniform spread density over the entire area of the glass substrate 10.

In addition, since the glass substrate 10 charged by the spread spacersis immediately subjected to discharging by the discharging bar, electriccharges are not stored in the glass substrate, thereby preventingswitching elements and the like in the conductive patterns 40 from beingelectrostatically broken down.

From the above, according to the spreading apparatus and the spreadingmethod of the present embodiment, spacers are uniformly spread on anglass substrate. With use of this glass substrate, it is possible toprovide liquid crystal display panels with high quality in which thedistance between two substrates is uniform over the entire substrates.

Note that the present invention is not limited to the embodiment asdescribed above, but can be variously modified within the scope of theinvention.

For example, the above-mentioned embodiment is arranged such that thesupply amount of the spacers from the spreading nozzle is reduced whenthe trace of the spreading nozzle passes each of folded portions of thetrace. However, the supply amount of the spacers from the spreadingnozzle may be continuously maintained at a constant value, and themoving speed or the angle speed of the spreading nozzle may be increasedby about 15% when the spreading nozzle passes each of the foldedportions of the trace. In this case, the spread amount of the spacersper unit area of the glass substrate can be reduced at each of thefolded portions of the trace, and the spacers can also be uniformlyspread as in the embodiment described above.

Further, the discharging means may be a soft X-ray ionizer rather than adischarging bar. In this case, the soft X-ray ionizer is capable ofeasily controlling the discharging area of the glass substrate, byshielding X-rays at portions where X-rays are not necessary. Besides,the air flow is not disturbed when the glass substrate is discharged bythe soft X-ray ionizer. Therefore, regions of the glass substrate wherespacers have yet to be spread can be subjected to discharging withoutinfluencing the on going spreading of the spacers.

As has been specified above, according to the present invention, spacerparticles can be uniformly spread onto a substrate so that it ispossible to provide a spreading method and a spreading apparatus whichare capable of easily manufacturing a liquid crystal display elementwith high display quality and high reliability.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

We claim:
 1. A method of spreading spacing particles on a surface of asubstrate used to form a liquid crystal display panel, the methodcomprising the steps of:relatively moving said substrate and a spreadingnozzle adapted to spread said spacing particles on said substrate withrespect to one another as said spreading nozzle spreads said spacingparticles such that said spacing particles spread from said spreadingnozzle form a predetermined trace on said surface of said substrate; anddischarging electric charge on said substrate while relatively movingsaid substrate and said spreading nozzle with respect to one anothersuch that said spreading nozzle spreads said spacing particles on adischarged portion of said surface of said substrate.
 2. A method ofspreading particles according to claim 1, wherein said spreading nozzlespreads said spreading particles at a spreading rate which is controlledin relation to a relative position of said substrate with respect tosaid spreading nozzle.
 3. A method of spreading particles according toclaim 1, wherein said substrate and said spreading nozzle are relativelymoved with respect to one another at a relative moving speed which iscontrolled in relation to a relative position of said substrate withrespect to said spreading nozzle.
 4. A method of spreading particlesaccording to claim 1, wherein folded portions of said trace comprise twosegments of said trace intersecting at an angle and said spreadingnozzle spreads said spacing particles at a spreading rate, saidspreading rate being reduced when said spreading nozzle is spreadingsaid spacing particles at each of the folded portions of said trace. 5.A method of spreading particles according to claim 1 wherein saidpredetermined trace is a zigzag trace.
 6. A method of spreadingparticles according to claim 4 wherein said predetermined trace is azigzag trace.
 7. A method of spreading particles according to claim 5,wherein said surface of said substrate has a pair of opposing side edgesand folded portions of the zigzag trace are located adjacent said sideedges.
 8. A method for spreading spacing particles according to claim 1wherein said discharging step includes relatively moving said substrateand a discharging device with respect to one another in a directionsubstantially parallel with a side edge of said substrate.